Device for compensating the weight of the heating plates in multistage presses with simultaneous closing mechanism



Sept. 23, 1969 SCHNElDER 3,468,243 DEVICE FOR COMPENSATING THE WEIGHT OF THE HEATING PLATES IN MULTISTAGE PRESSES WITH SIMULTANEOUS CLOSING MECHANISM Filed D86. 29, 1966 3 Sheets-Sheet l F/Q/TZ JC/V VF/DZI? y 67 TOE/V) Sept. 23, 1969 F. SCHNEIDER 3,468,243 DEVICE FOR COMPENSATING THE WEIGHT OF THE HEATING PLATES IN MULTISTAGE PRESSES WITH SIMULTANEOUS CLOSING MECHANISM Filed Dec. 29, 1966 s Sheets-Sheet 2 fR/TZ -SC //Vz. /DL /P 67 5, 4 01/01,

Sept. 23, 1969 Filed Dec. 29,

F. SCHNEIDER DEVICE FOR CQMPENSATING THE WEIGHT OF THE HEATING PLATES IN MULTISTAGE PRES WITH SIMULTANEOUS CLOSING MECHANI 5 Sheets-Sheet 5 ACCUMUL/J 7'01? IIVI ENTOP MAW A fro QA E/ United States Patent 3,468,243 DEVICE FOR COMPENSATING THE WEIGHT OF THE HEATING PLATES IN MULTISTAGE PRESSES WITH SIMULTANEOUS CLOSING MECHANISM Fritz Schneider, Krefeld, Germany, assignor to Niederrheinische Maschinenfabrik Backer & van Hullen, Krefeld, Germany Filed Dec. 29, 1966, Ser. No. 605,642 Claims priority, application Germany, Jan. 3, 1966, N 27,840 Int. Cl. B30b 7/02; B29c 3/00; B27d 3/00 US. Cl. 100200 2 Claims ABSTRACT OF THE DISCLOSURE A device for compensating the weight of the heating plates in a multi-stage press with a simultaneous closing mechanism comprising a plurality of press plates vertically displaceable in the frame, a pair of fork-like arms, each pivoted to the frame, and rods pivoted to the arms and to the press table. Tension members are pivoted to the arms and to the press plates. The tension members are constituted by pneumatic work-cylinders having enlarged and reduced cylinder portions. Supply conduits for the pressure medium and adjusting valves are provided.

The present invention relates to a device for compensating the weight of the heating plates in a multistage press with simultaneous closing mechanism.

Particularly where such multi-stage presses are used for making laminated plates, it is often necessary to provide the same specific pressure conditions in all press stages, in order to produce perfect laminated plates. This is the case especially where there are no spacing bars between the stages for the pressing, 'which fix the stage spacing accurately for the pressing process.

The known art has developed mechanisms of Widely varying constructions for the simultaneous opening and closing of all stages of multi-stage presses. Amongst these constructions the most successful comprises on two op posite sides on the upper press stay always one arm aranged to pivot about a horizontal axis, and on the lower liftable and lowerable stay (press table) a push rod, articulately engaging the free end of the associated pivoting arm, and wherein the individual stage plates are articulately connected with the pivoting arms by means of tension members. These tension members engage the associated pivoting arm in the sequence of the stage plates, taken from the top towards the bottom, in proportionally increasing distances.

In order to fit the individual tensioning members in their constructionally fixed length between the points of articulation at the associated stage plate and the pivoting arm, a tightener or similar tightening device is usually provided on each tension member. After completed adjustment of the tension members to their relative lengths, the mechanism of the type described hereinbefore Would work perfectly, if all stages of the press were always to receive charges in the same height and if the stages were accurately set during the assembly. However, it is well known that this is not the case in practice. It must always be expected that one stage will have a higher or lower charge, or that it may even remain empty by mistake, apart from the fact that the exact setting of the stages is impossible.

In order to avoid the difiiculties, resulting from these facts during the pressing of plates, it is already known to equip each of the said tension members between the stage plate and the associated pivoting arm with a hydraulic balancing mechanism. Such a balancing mecha- 3,468,243 Patented Sept. 23, 1969 nism consists of a working cylinder and a hollow piston, wherein the hollow piston is affected by a hydraulic medium only in the direction towards the associated pivoting arm and is also equipped with a bottom-fitted bush for the enlarged upper end of the tension member.

With these balancing devices, the same specific pressure conditions can be obtained in all press stages only if the lowermost press stage, that is to say, the stage between the table and the next higher press stage, remains unoccupied. Only then is there the possibility of fully compensating the heating plate weight of the press stages by means of the said balancing mechanism.

The invention, based on such a known multistage press, has the object of providing such a device for compensating the weight of the heating plates such that the operation of the press is possible even if the lowermost stage is occupied.

According to the invention, this object may be realized in that there is provided for the hollow piston a hydraulic abutment in the form of a piston which may carry out a limited movement in the working cylinder, and in that this abutment may be rendered inoperative during the closure of the press and during the actual pressing.

According to another feature of the invention, the working cylinder is a stepped cylinder, wherein the shoulder forms the limit stop for the piston serving as counterabutment.

Furthermore, according to the invention, the effective surface of the counter-abutment piston is larger than that of the hollow piston. In this way, both pistons can be actuated under the same pressure from a common oil accumulator. However, in view of the larger effective surface of the counter-abutment, the effective force thereof is larger in the engaged condition, so that the counter-abutment piston cannot be forced away from the hollow piston.

In view of the connection to a common oil accumulator, this design requires two conduits for the hydraulic medium for the pressure chamber of the counter-abutment, namely a feed and a return conduit, adapted to be closed by valves. Preferably, these valves will have the form of magnetic valves.

The invention will be further explained with reference to the accompanying drawing, in which:

FIG. 1 is a partly sectionalized front elevation of the press, shown in the left half of the drawing in the open state and in the right half in the closed state;

FIG. 2 is a side elevation of the press in the open state; and

FIG. 3 is an axial cross-section of a hydraulic working cylinder of a balancing device with counter-abutment piston.

In a multi-stage press, the upper press stay 2 is fixed stationarily to a main frame 1, and the lower stay, forming a press table 3, is mounted so that it can be raised and lowered, as known in the art; hydraulic cylinders 4 are provided for the upwardly directed working stroke of the press table 3, and its subsequent return for opening the press. Read from the top to the bottom, the reference numerals, 5, 6a, 6b, 6c, 6d. 7 signify the plates of the individual press stages the plates with the press in open condition and 6 and 7, the plates with the press in closed condition, and the reference numerals 6a. For the sake of clarity, the drawing shows only six such press stages, whilst in practice their number may exceed twenty. As known in the art, the top plate 5 of the uppermost stage is connected rigidly with the upper stay 2, and the bottom plate '8 of the lowermost stage rigidly with the press table 3.

At each longitudinal side of the press, the stay 2 carries two fork-like arms 9, each pivotable about a horizontal axis 10. A rigid rod 12 is artieulately connected with the free end of each arm 9 as at 11, and its lower end is articulated as at 13 to the press table. For lifting and retaining the stage plates 6 and 7 (which may also rest on abutments of the frame 1 when the press is opened) there are provided tension members in the form of rods 14, connected articulately with the associated stage plate at 15.

Each tension rod 14 has a tightener or like device 16, enabling it to be adjusted to its exact constructional length, as well as a balancing device, shown generally at 17. The piston-shaped enlarged upper end 18 of each rod 14 is guided in a bush-like cavity 19 of a piston 20 (FIG. 3). The said piston 20 is mounted displaceably in a working cylinder 21 and passes with its lower portion 20a, forming the guide for the associated rod 14, through the lower end wall 21a of the cylinder 21. The upper end wall 21b of the cylinder carries an eyelet 22, by means of which the cylinder 21, and thus also the rod 14, connected therewith via the hollow piston 20 and the rod end 18, is articulately connected at 23 with the asociated pivot arm 9 (see FIG. 1).

At the point where its cavity 19 passes from the bushlike portion into the lower portion forming the guide for the rod 14, the hollow piston 20 forms a shoulder 20b, on which the piston-shaped upper end 18 of the rod 14 normally rests. The working chamber 210 of the cylinder 21, left free by the piston 20, may be affected by a hydraulic medium via a conduit 24, so that the medium act from the bottom, i.e., in the direction towards the associated pivoting arm 9, on the piston 20. It may be easily achieved by suitable piston seals 25 that the hydraulic medium cannot escape either towards the top into the cavity 19, or towards the bottom from the working chamber of the cylinder 21.

The working cylinder 21 is a stepped cylinder so that its upper portion forms a working chamber 21d with a larger cross-section than the chamber 210. A piston 26 is guided in this portion 21d and forms a counter-abutment for the hollow piston 20. The working chamber 21d communicates with a conduit 27 which forks into a part 27a and a part 27b. In each fork 27a and 27b, there is a valve 28a and 2811, respectively, for example, in the form of a magnetic valve.

The conduits 24 and 27]; lead to a common oil accumulator. Since the eflective surface of the counterabutment piston 26 is substantially larger than that of the piston 20, the piston 26 forms, in the case of bilateral actuation, an abutment for the piston 20.

However, the downward movement of the piston 26 in the cylinder 21 is limited by a shoulder 21c.

The operation of the device according to the invention is as follows:

When the press is closed from the fully open state, the supply conduits 24 and 27b are under the same pressure. The valve 28a is open, whilst the valve 28b is closed. Thus, the same pressures prevail in the press chambers 21c and 21d. Owing to the cross-sectional ratios between the effective surfaces of the pistons 20 and 26, the piston 26 becomes a counter-abutment for the piston 20, which can accordingly only move up to the lower surface of the piston 26. The force of the piston 20 is so adjusted by '4 means of the actuating pressure that it exceeds the weight of the plates including the weight of the material to be pressed in the individual press stages.

After the termination of the closing movement and the starting of the actual pressing at a higher pressure, the. balancing mechanism 17 is switched by means of a control device, not shown. The valve 28a closes and the valve 28b opens so that the press chamber 21d is depressurized and the counter-abutment becomes ineffective. This releases the fixing of the piston 20 and the same assumes in each case a position in which the piston-like ends 18 of the rods 14 rest on the shoulder 20b of the piston 20, causing the weight of the heating plates to be fully balanced.

For opening the press, the counter-abutment is again actuated by pressurizing the piston 26, whereby the simultaneous opening of the press is assured.

I claim:

1. A device for compensating the weight of the heating plates in a multistage press with simultaneous closing mechanism comprising a press frame, a vertically displaceable press table in said press frame, means for vertically displacing said press table, a plurality of press plates vertically displaceable in said frame, a pair of forklike arms, each pivoted with one of its ends about a horizontal axis to opposite sides of said frame, a pair of rigid rods pivoted with one of their ends to the free ends of said arms, respectively, and with their other ends to opposite ends of said press table, a plurality of tension members spacedly pivoted with upper ends to the respective arms and with their lower ends to the press plates, said tension members comprising a rod having an upper piston-shaped enlarged end, a work cylinder having a reduced lower portion and an enlarged upper portion, a hollow piston slidable in said reduced lower portion and forming a first chamber therewith and having a bush-like portion extending through the bottom wall of said cylinder for guiding said piston-shaped end of said rod, a solid piston slidable in said enlarged upper portion, and forming a second chamber therewith, said solid piston forming a counter-abutment for said hollow piston, a first supply conduit means for pressure medium for said first chamher, a second supply conduit means for said second chamber and valve means for opening and closing the supply conduit means to said second chamber.

2. A device as claimed in claim 1, wherein said work cylinder is provided with a shoulder portion forming a limit stop for said solid piston.

References Cited UNITED STATES PATENTS 2,913,027 11/1959 Thurnher 144281 3,361,056 l/1968 Carlsson et al 200 FOREIGN PATENTS 1,419,334 10/1965 France.

BILLY J. WILHITE, Primary Examiner US. Cl. X.R. l816; 144-281 

